Debt - Schedule of Total Interest Expense on Convertible Senior Notes (Detail) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 853,000	$ 841,000
Accretion of debt discount (Non-cash)			2,753,000	1,972,000
Senior Convertible Notes
Debt Instrument [Line Items]
Contractual interest expense (Cash)	2,138,000	2,139,000	6,415,000	4,657,000
Amortization of debt issuance costs	232,000	216,000	684,000	465,000
Accretion of debt discount (Non-cash)	907,000	843,000	2,671,000	1,816,000
Total interest expense	3,277,000	3,198,000	9,770,000	6,938,000
Effective interest rate of the liability component	7.32%	7.32%	7.32%	7.32%
Fair Value, Inputs, Level 1 | Senior Convertible Notes
Debt Instrument [Line Items]
Fair Value of principal amount of notes	$ 202,000,000		$ 202,000,000